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5 December 2013 11:26 am ,
Vol. 342 ,
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Transgenic Calves Cloned
22 May 1998 6:30 pm
Scientists have cloned three calves that carry a foreign gene. The success, described in today's Science, opens the field for herds of transgenic cows that could produce copious amounts of milk rich in therapeutic proteins.
The standard way to create an animal with an extra gene is to inject the DNA into a fertilized egg. But most times the gene is not expressed and so the adult animal doesn't produce the desired protein. An alternate strategy is to first add the gene to the nucleus of a cell that development has specialized, then tuck that nucleus into an egg whose own nucleus has been removed. Last December, scientists succeeded in modifying sheep fetal cells this way to carry the gene for Human Factor IX, which some hemophiliacs take to aid blood clotting.
Now the same cloning technique has been applied to cows, which give much more milk. The researchers--James Robl, a developmental biologist and his colleagues at the University of Massachusetts at Amherst, and Steve Stice at Advanced Cell Technology in Worcester, Massachusetts--inserted a marker gene fused with a gene for resistance to the chemical neomycin into a culture of connective tissue cells called fibroblasts. Then they added neomycin to kill cells that hadn't taken up the gene combo. Those that survived developed into embryos, 28 of which were implanted into 11 cows; three gave birth to genetically identical calves, all of which carried the neomycin-marker gene.
Robl and Stice, in collaboration with the biotech company Genzyme of Cambridge, Massachusetts, have already created embryos that contain the human gene for albumin protein, which helps restore the blood's osmotic pressure after blood loss. "Albumin is at the top of everyone's list" of genes to clone into a cow," says Stice. A single cow could produce 80 kilograms of the protein a year, he says.
"This is very exciting study," says Randall Prather, a developmental biologist at the University of Missouri at Columbia. The neomycin strategy allows researchers to make sure that the gene is functioning properly before it's inserted into a cow, he says.